Abstract: The Jingshansi iron deposit in Henan Province is located in the southeastern part of the North China Craton. The orebodies occur in nearly bedded and lenticular forms, and the iron ores are predominantly banded, with minor massive ones. Taihua Group Tieshanmiao Formation marbles are developed as main wall rocks and interlayers among the orebodies. Geochemical studies of carbon, oxygen and silicon isotopes of the ore deposit were carried out to investigate the ore-forming fluid nature and its potential sources. The results show that δ¹³C_V-PDB values of ore-forming calcite range from-5.2‰ to-1.4‰, δ¹⁸O_V-SMOW values range from8.5‰ to 16.9‰, δ¹³C_V-PDB values of carbonate host rocks calcite range from-1.0‰ to 1.6‰, and δ¹⁸O_V-SMOW values range from 20.3‰to 23.4‰, the C and O isotope evolution indicates that drastic water-rock interaction took place at the ore-forming stage, and isotope exchange took place between ore-forming fluids and carbonate host rocks. The carbon isotope components were mainly provided by the marine carbonate rocks through dissolution, influenced by middle-low temperature alteration. The characteristics of δ¹⁸O_H2O hydrothermal solution is the mixture of magmatic water and seawater. The 2Oindicate that the δ³⁰Si_NBS-28 values of iron ore quartz range from-1.9‰ to-0.4‰, and the δ³⁰Si value of leptite quartz is 0‰, which indicates that the silicon isotope were derived from volcanic exhalation. The Si isotope fractionation took place in the ore-forming process. A comprehensive analysis shows that the Jingshansi iron deposit was formed in a submarine volcanic eruptions-sedimentary environment in Precambrian.